Global Importance of Diarrhieal Diseases and Malnutrition

Abstract

The amount of new knowledge accumulated in the past 15 years about the aetiology, epidemiology, and public significance of diarrhoeal disease is quite remarkable, particularly because such knowledge has challenged orthodox concepts strongly rooted in misconceptions. Until recently, most diarrhoeas in the general population were regarded as 'food indigestion' and accordingly were given a variety of lay names. Remarkably, even today some medical professionals may refer to certain diarrhoeas as caused by unwholesome food with characteristics incompatible with health. Even though shigellosis, salmonellosis, cholera, giardiasis, amoebiasis, and other specific clinical entities had been characterized satisfactorily, as recently as 10 years ago it was difficult to prove that most outbreaks of diarrhoea in communities were of an infectious origin. In fact, some spoke of 'nutritional diarrhoea' in analogy with nutritional anaemias. It is now accepted, however, that most diarrhoeas in the community and in outpatient and emergency hospital services are related to viral, microbial, and parasitic agents, a concept supported by the following considerations: (a) diarrhoeas are prevalent in ecosystems with inadequate environmental sanitation, education, income, and personal hygiene; (b) secondary cases develop in contacts of index cases within intervals compatible with incubation periods, pointing to spread by direct or indirect contact; (c) incidence and severity of diarrhoea decrease with age, and older persons are relatively free of diarrhoea, suggesting the d!..relopment of immunity; (d) comprehensive laboratory investigations demonstrate a potential infectious pathogen in about 70 per cent of acute diarrhoea cases (Mats 1983a). Thus, improvement of personal hygiene and environmental sanitation results in a significant reduction in morbidity and mortality due to diarrhoeal diseases. It is easy to understand the epidemic proportions of diarrhoea in New York City at the turn of the century, comparable to that of many less developed countries today, when environmental conditions, education, personal hygiene, and income were low, especially among immigrants.